KR101605901B1

KR101605901B1 - Air conditioner and control method thereof

Info

Publication number: KR101605901B1
Application number: KR1020090086152A
Authority: KR
Inventors: 최환종; 정승현; 류병진
Original assignee: 엘지전자 주식회사
Priority date: 2009-09-11
Filing date: 2009-09-11
Publication date: 2016-03-23
Also published as: WO2011031014A2; KR20110028180A; EP2299206B1; EP2299206A1; WO2011031014A3; CN102022807A; CN102022807B

Abstract

The present invention relates to an air conditioner and a control method thereof, and more particularly, to an air conditioner for controlling an induction heater by detecting a cone amount of a heat exchanger and a control method thereof.

An air conditioner according to an embodiment of the present invention includes: a compressor for compressing a refrigerant; An indoor heat exchanger for exchanging the refrigerant passing through the compressor with indoor air; An expansion device for reducing the pressure of the refrigerant passing through the indoor heat exchanger; An outdoor heat exchanger for exchanging heat with the refrigerant discharged from the expansion device; A plurality of sensors for sensing a temperature of the outdoor air and a temperature of the outdoor heat exchanger; A heater having a variable heating value according to the outdoor air temperature sensed by the sensor and the outdoor heat exchanger temperature; And a control unit for controlling the output of the heater in accordance with the landing amount and determining the landing amount of the outdoor heat exchanger according to the temperature difference between the outdoor air temperature and the outdoor heat exchanger.

According to the air conditioner of the present invention, since the amount of heat of the induction heater can be adjusted according to the indoor / outdoor temperature and the temperature of the outdoor heat exchanger, power consumption can be reduced.

Gas-liquid separator, induction heater, outdoor temperature

Description

[0001] The present invention relates to an air conditioner and a control method thereof,

An embodiment according to the present invention relates to an air conditioner and a control method thereof.

The present invention relates to an air conditioner and a control method thereof, and more particularly, to an air conditioner for controlling an induction heater by detecting a cone-shaped amount of an outdoor heat exchanger and a control method thereof.

Generally, an air conditioner is a household appliance for keeping indoor air in a most suitable state according to purpose and purpose. For example, in the summer, the room is cooled and the room is warmed. In winter, the room is warmed, and the humidity in the room is controlled. The air in the room is kept clean and comfortable.

As convenience products such as air conditioners are gradually expanded and used, consumers are demanding high energy efficiency, products that are convenient for performance improvement and use.

Such an air conditioner is divided into a separate type air conditioner in which the indoor unit and the outdoor unit are separated from each other, and an integrated type air conditioner in which the indoor unit and the outdoor unit are combined into one unit. According to the installation mode of the air conditioner, the air conditioner is divided into a wall-mounted type air conditioner and a framed type air conditioner, and a slim type air conditioner configured to stand on a living room.

The separate type air conditioner includes an indoor unit installed in a room to supply hot air or cold air into the air conditioning space, and an outdoor unit for compressing and expanding refrigerant so that a sufficient heat exchange operation can be performed in the indoor unit.

Meanwhile, in the conventional heating operation of the air conditioner capable of cooling and heating, when a cone is generated on the surface of the outdoor heat exchanger by a temperature sensor provided in the outdoor heat exchanger, the inverter compressor is led to a low frequency, And then the cooling cycle was temporarily activated to remove the implantation.

However, when such a method is used, the indoor heat exchanger functions as an evaporator, and since the defrosting is required in the cooling state, the room temperature is lowered.

Further, the operation of the air conditioner is switched, and accordingly, the high-temperature refrigerant is supplied to the outdoor heat exchanger, so that the defrosting time required for the defrosting is somewhat increased.

An embodiment of the present invention relates to an air conditioner and a control method thereof, and more particularly, to an air conditioner and control method thereof for improving the structure and control of an air conditioner so as to efficiently perform heating and defrosting .

It is also an object of the present invention to provide an air conditioner and a control method thereof for detecting the amount of impregnation of a heat exchanger and varying the amount of heat of the induction heater.

According to an aspect of the present invention, there is provided an air conditioner including: a compressor for compressing a refrigerant; An indoor heat exchanger for exchanging the refrigerant passing through the compressor with indoor air; An expansion device for reducing the pressure of the refrigerant passing through the indoor heat exchanger; An outdoor heat exchanger for exchanging heat with the refrigerant discharged from the expansion device; A plurality of sensors for sensing a temperature of the outdoor air and a temperature of the outdoor heat exchanger; A heater having a variable heating value according to the outdoor air temperature sensed by the sensor and the outdoor heat exchanger temperature; And a control unit for controlling the output of the heater in accordance with the landing amount and determining the landing amount of the outdoor heat exchanger according to the temperature difference between the outdoor air temperature and the outdoor heat exchanger.

In another aspect of the present invention, there is provided a method of controlling an air conditioner, the method comprising: comparing a room temperature with a preset first preset temperature; Comparing the outdoor temperature with a preset second preset temperature according to the indoor temperature; Determining a temperature difference value between the outdoor temperature and the outdoor heat exchanger; Comparing the temperature difference value with a preset reference temperature value; And adjusting a calorific value of the heater according to a result of the comparison of the temperature difference value and the reference temperature value.

According to the embodiment of the present invention as described above, the indoor heating performance is increased by the continuous heating and defrosting operation in which heating and defrosting are simultaneously performed, and the conception of the outdoor heat exchanger can be eliminated.

In addition, the amount of irrigation of the outdoor heat exchanger can be determined according to the indoor / outdoor temperature and the temperature of the outdoor heat exchanger, and the amount of heat of the induction heater can be varied according to the determined irrigation amount, thereby reducing unnecessary power consumption .

Further, since the induction heater is provided in the accumulator, the amount of heat transferred to the outside air is reduced, and the time required for heat transfer from the induction heater to the refrigerant is reduced.

In addition, the heating performance can be improved without additionally increasing the output of the compressor by applying heat to the low-pressure side refrigerant in the heating cycle from the induction heater during the heating process.

Further, in the defrosting process for removing the frost formed on the evaporator, by operating the induction heater, a greater amount of heat can be transferred to the low-pressure side refrigerant, thereby improving defrost performance of the air conditioner.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. It is to be understood, however, that the spirit of the invention is not limited to the embodiments shown and that those skilled in the art, upon reading and understanding the spirit of the invention, may easily suggest other embodiments within the scope of the same concept.

1 is a view showing a configuration of a heating cycle of an air conditioner according to an embodiment of the present invention.

Referring to FIG. 1, an air conditioner 1 according to an embodiment of the present invention includes a compressor 10 for compressing a refrigerant, a refrigerant compressed by a high temperature and high pressure by the compressor 10, An indoor fan (22) for blowing heat-exchanged warm air into the room, a capillary (30) as an expansion device for expanding the heat-exchanged refrigerant to a low pressure, an indoor heat exchanger An outdoor heat exchanger 41 for exchanging heat with outdoor air, and an outdoor fan 42 for blowing heat-exchanged cold air to the outside.

In detail, when a heating cycle is performed through the air conditioner, a condenser for condensing the refrigerant compressed through the compressor 10 to a low temperature is applied to the indoor heat exchanger 21, and the outdoor heat exchanger 41, An evaporator for evaporating the liquid refrigerant decompressed through the capillary 30 is applied.

Here, a high pressure is formed before the refrigerant circulating in the heating cycle passes through the capillary 30, and a low pressure is formed after passing through the capillary 30. Hereinafter, the refrigerant before passing through the capillary 30 is called a high-pressure side refrigerant, and after passing through it is called a low-pressure side refrigerant.

A gas-liquid separator (50) is provided at the discharge side of the outdoor heat exchanger (41) so that only the gas refrigerant in the refrigerant evaporated through the outdoor heat exchanger (41) flows into the compressor (10).

A refrigerant hot gas that has passed through the compressor 10 is bypassed to the inlet side of the outdoor heat exchanger 41 or the inlet side of the gas-liquid separator 50 to the air conditioner 1, A bypass flow path 81 is provided. That is, the bypass passage 81 extends from the outlet side of the compressor 10 to the inlet side of the outdoor heat exchanger 41 and the inlet side of the compressor 10.

The bypass passage 81 is provided with a first valve 80 for controlling the flow rate of refrigerant to be bypassed. The first valve (80) may include a solenoid valve.

The refrigerant having passed through the compressor 10 is bypassed to the inlet side of the compressor 10 so that the evaporation temperature and pressure of the refrigerant at the inlet side of the compressor 10 can be raised, There is an advantage that the input date (load) In addition, the imbalance generated between the capacity of the compressor (10) and the capacity of the indoor heat exchanger (21) is eliminated and the heating efficiency can be increased.

The refrigerant of high temperature and high pressure that has passed through the compressor 10 is bypassed to the inlet side of the outdoor heat exchanger 41 so that defrosting of the outdoor heat exchanger 41 can be performed.

As described above, since the refrigerant is bypassed by the first valve 80, the heating and defrosting can be simultaneously performed. This type of operation is called continuous heating defrosting.

The first bypass passage 81 is provided with a second valve 90 for preventing the refrigerant from flowing from the inlet side of the outdoor heat exchanger 41 to the inlet side of the gas-liquid separator 50. The second valve (90) prevents the refrigerant from flowing backward from the inlet side of the outdoor heat exchanger (41) to the inlet side of the gas-liquid separator (50) in the normal heating mode of the air conditioner. The second valve (90) may include a check valve.

A four-way valve (70) is provided on the discharge side of the compressor (10) for switching the flow direction of the refrigerant according to the cooling or heating mode of the air conditioner. In the heating mode, the refrigerant having passed through the outdoor heat exchanger (41) flows into the compressor (10) through the four-way valve (70) and is compressed. The compressed refrigerant passes through the four- And then flows into the indoor heat exchanger (21). On the other hand, in the cooling mode, the refrigerant that has passed through the indoor heat exchanger 41 is introduced into the compressor 10 via the four-way valve 70 and then compressed. The compressed refrigerant passes through the four- To the outdoor heat exchanger (41).

On the other hand, an induction heater 100 for heating the refrigerant of the gas-liquid separator 50 is provided outside the gas-liquid separator 50. The induction heater 100 may be disposed to surround the outer circumferential surface of the gas-liquid separator 50.

Here, the induction heater 100 is a heater using an induction current generated by a magnetic field as a heat source, and is composed of an electromagnet through which a high frequency alternating current can pass. The electromagnet includes a coil through which an alternating current flows.

The induction heater 100 may provide a heat quantity to the low-pressure side refrigerant, that is, the refrigerant at the side of the outdoor heat exchanger 41 in the continuous heating defrosting mode to raise the evaporation temperature of the refrigerant and help remove the frost frost . Also, the induction heater 100 may increase the condensation temperature by supplying heat to the high-pressure side refrigerant, that is, the refrigerant at the indoor heat exchanger 21 side. As described above, the evaporation temperature and the condensation temperature of the refrigerant are increased by the induction heater 100, so that the heating efficiency can be improved and the defrost efficiency can be improved.

In addition, the induction heater 100 provides the amount of heat to the indoor heat exchanger 21 side in the general heating mode to raise the temperature of the piping of the indoor heat exchanger 21, thereby increasing the temperature of the air taken into the indoor space It has the effect of being able to increase quickly.

Meanwhile, the induction heater 100 may be applied with an inverter method in which the amount of heat supplied from the heater 100 is controlled. In this case, there is an advantage that the amount of heat can be variably supplied according to the temperature of the outside air and the temperature of the heat exchanger requiring defrost. The control method in which the amount of heat generated by the induction heater 100 is varied according to the amount of the frosting of the outdoor heat exchanger 41 will be described later with reference to the drawings.

2 is a block diagram showing the configuration of an air conditioner according to an embodiment of the present invention.

2, the air conditioner 1 according to the embodiment of the present invention includes an outdoor temperature sensor 110 for detecting the temperature of the outside air, a room temperature sensor 120 for detecting the temperature of the indoor space, An outdoor heat exchanger sensor 130 for sensing a refrigerant pipe temperature of the outdoor heat exchanger 41, an induction heater 60 for generating a variable heat based on the sensed values of the sensors 110, 120 and 130, And a control unit 100 for controlling the sensors 110, 120, and 130. The outdoor temperature sensor 110, the indoor temperature sensor 120 and the outdoor heat exchanger sensor 130 are respectively referred to as a "first temperature sensor", a "second temperature sensor" and a "third temperature sensor" .

In detail, the sensed values of the sensors 110, 120 and 130 are transmitted to the controller 100, and the controller 100 reads the information of the sensors 110, 120 and 130 to determine the amount of heat of the induction heater 60 As shown in FIG.

In the following description, the value of the outdoor temperature-outdoor pipe temperature is referred to as "GAP ", and the magnitude of the heat output from the induction heater 60 can be divided into P1, P2 or P3 Let us know. However, the amount of heat that can be output according to the control method of the induction heater 60 may be more variously provided.

FIG. 3 and FIG. 4 are flowcharts showing a method of controlling the air conditioner according to an embodiment of the present invention with respect to a first interval of the room temperature, and FIG. 5 is a flowchart illustrating a method in which the air conditioner is controlled &Lt; / RTI >

3 to 5, a control method of an air conditioner according to an embodiment of the present invention will be described. The flow charts shown in Figs. 3 to 5 explain the control method in the process of performing the continuous heating defrosting operation.

3 and 4 illustrate a control method of the induction heater according to the outdoor temperature and the outdoor pipe temperature when the room temperature is T1 or more. FIG. 5 shows a method of controlling the induction heater according to the outdoor temperature and the outdoor pipe temperature, Fig. Here, the temperature T1 is a predetermined temperature and can be formed at about 15 deg. Of course, the T1 may be set to a different value according to the control method of the air conditioner.

First, the room temperature is sensed by the room temperature sensor 120 (S11). If the room temperature is T1 or more, the outdoor temperature is detected by the outdoor temperature sensor 110, and it is determined whether the outdoor temperature is greater than T2 (S12, S13, S14). Here, T2 may be a predetermined temperature and may be formed at about 0 占 폚. Of course, the T2 may be set to a different value according to the control method of the air conditioner.

If the outdoor temperature is equal to or higher than T2, the congestion amount of the outdoor heat exchanger 41 is determined (S15). That is, it is judged whether or not "GAP" (outdoor temperature-outdoor pipe temperature) is formed larger than H1. Here, the larger the GAP, the greater the amount of air to be condensed in the piping of the outdoor heat exchanger, and thus the greater the tendency to be conceived on the piping.

In detail, the refrigerant pipe temperature of the outdoor heat exchanger 41 is sensed by the outdoor heat exchanger sensor 130, and the controller 100 determines a difference value (GAP) of the refrigerant pipe temperature at the outdoor temperature . At this time, the difference value is compared with the H1 value (S16). Here, the H1 may be formed at about 8 DEG C as a preset temperature difference value. Of course, the H1 may be set to a different value according to the control method of the air conditioner.

When the GAP is greater than H1, the control unit 100 determines that the amount of fusing of the outdoor heat exchanger 41 is large, and accordingly, the output of the induction heater 60 Can be adjusted to P1 (first output value). Here, the P1 may be formed at a predetermined output value of about 1200 W (S20).

On the other hand, if the GAP has a value greater than H2 and less than or equal to H1, the control unit 100 determines that the amount of fusing of the outdoor heat exchanger 41 is at an ordinary level, and thus the output of the induction heater 60 is P2 (Second output value).

Here, H2 is a predetermined temperature difference value, which is different from H1 at about 4 DEG C, and P2 is a predetermined output value and can be formed at about 900W smaller than P1. Of course, the H2 and P2 may be set to different values according to the control method of the air conditioner (S17, S19).

On the other hand, if it is determined that the GAP is smaller than H2, the controller 100 determines that the amount of fusing of the outdoor heat exchanger 41 is small, and accordingly, the amount of heat generated by the induction heater 60 is reduced. And the output of the heater 60 can be adjusted to P3 (third output value). Here, the P3 may be formed at about 600 W as a preset output value. However, the P3 may be set to another output value smaller than P2 according to the control method of the air conditioner (S17, S18).

If it is determined in step S14 that the outdoor temperature is equal to or lower than T2, it is determined whether the outdoor temperature is higher than T3 and lower than T2 as shown in FIG. 4 (S21). Here, T3 may be formed at about -5 [deg.] C, but it may be set to a different temperature value according to the control method.

If the outdoor temperature is greater than T3 and equal to or lower than T2, the congestion amount of the outdoor heat exchanger 41 is determined (S22). The implantation amount is determined according to whether or not the GAP is formed larger than H3.

In detail, the refrigerant pipe temperature of the outdoor heat exchanger (41) is sensed by the outdoor heat exchanger sensor (130), and the controller (100) senses the outdoor temperature and the refrigerant pipe temperature of the outdoor heat exchanger (41) . At this time, the difference value is compared with the H3 value (S23). Here, the H3 may be formed at a predetermined temperature difference value of about 6 DEG C different from the H1 and H2. Of course, the H3 may be set to a different value according to the control method of the air conditioner.

When the GAP is larger than H3, the control unit 100 determines that the amount of fusing of the outdoor heat exchanger 41 is large, and accordingly, the output of the induction heater 60 is increased so that the amount of heat generated by the induction heater 60 can be increased. Can be adjusted to P1 (S20).

On the other hand, when the GAP is greater than H4 and equal to or less than H3 (S24), the controller 100 determines that the amount of the outdoor heat exchanger 41 is at the normal level, The output can be adjusted to P2 (S19). Here, the H4 may be formed at about 3 DEG C as a preset temperature difference value. Of course, H4 may be set to a different value according to the control method of the air conditioner.

On the other hand, if it is determined that the GAP is less than H4 (S24), the control unit 100 determines that the amount of fusing of the outdoor heat exchanger 41 is small and accordingly the amount of heat generated by the induction heater 60 may be reduced The output of the induction heater 60 may be adjusted to P3 (S18).

In step S21, if the outdoor temperature is equal to or lower than T3, an implantation amount can be determined (S25). The implantation amount is determined according to whether or not the GAP is formed larger than H5. Here, the H5 may be formed at about 7 DEG C as a preset temperature difference value. Of course, H5 may be set to a different value according to the control method of the air conditioner.

When the GAP is larger than H5 (S26), the control unit 100 determines that the amount of fusing of the outdoor heat exchanger 41 is large, and accordingly the induction heater 60 Can be adjusted to P1 (S20).

On the other hand, if the GAP has a value of H5 or lower (S26), the controller 100 determines that the amount of fusing of the outdoor heat exchanger 41 is at an ordinary level, and accordingly, the output of the induction heater 60 is P2 (S19).

As the GAP is within a predetermined range and the outdoor temperature is low, generally, the amount of irrigation is large and the amount of heat required to remove the frost is higher. When the outdoor temperature is lower than T3, the amount of heat of the induction heater 60 At least at the P2 level.

If the room temperature is lower than T1 in step S12, the outdoor temperature value is determined as shown in FIG. 5 (S31). Specifically, the outdoor temperature is sensed by the outdoor temperature sensor 110, and the controller 100 determines whether the outdoor temperature is greater than T2 (S32). As described above, the T2 may be formed at about 0 deg. C as a preset temperature.

If the outdoor temperature is higher than T2, the congestion amount of the outdoor heat exchanger 41 is determined (S22). The implantation amount is determined according to whether or not the GAP is formed larger than H6 (S33). Here, the H6 may be formed at about 7 DEG C as a preset temperature difference value. Of course, H6 may be set to a different value according to the control method of the air conditioner.

When the GAP is greater than H6 (S34), the control unit 100 determines that the amount of fusing of the outdoor heat exchanger 41 is large, and accordingly the induction heater 60 Can be adjusted to P1 (S20).

On the other hand, when the GAP has a value of H6 or less (S34), the controller 100 determines that the amount of the outdoor heat exchanger 41 is at the normal level, and accordingly, the output of the induction heater 60 P2 (S19).

On the other hand, if it is not determined in step S32 that the outdoor temperature is greater than T2, it is determined whether the outdoor temperature is higher than T3 and lower than T2 (S37). If it is determined that the outdoor temperature is higher than T3 and lower than T2, the controller 100 determines an implantation amount (S38).

In detail, the control unit 100 determines whether the GAP is greater than H7 (S39). Here, the H7 may be formed at about 6 DEG C as a preset temperature difference value. Of course, the H7 may be set to a different value according to the control method of the air conditioner.

If the GAP is determined to be greater than H7, the control unit 100 determines that the amount of fusing of the outdoor heat exchanger 41 is large, and accordingly, the induction heater 60, Can be adjusted to P1 (S20).

However, if it is determined that the GAP is equal to or lower than H7, the controller 100 determines that the amount of the outdoor heat exchanger 41 is normal and adjusts the output of the induction heater 60 to P2 S19).

In step S37, if the outdoor temperature is equal to or lower than T3, an implantation amount can be determined (S40). The implantation amount is determined according to whether or not the GAP is formed larger than H8. Here, the H8 may be formed at about 5 DEG C as a preset temperature difference value. Of course, the H8 may be set to a different value according to the control method of the air conditioner.

When the GAP is greater than H8 (S41), the control unit 100 determines that the amount of fusing of the outdoor heat exchanger 41 is large, and accordingly the induction heater 60 Can be adjusted to P1 (S20).

If the GAP has a value equal to or less than H8 (S26), the control unit 100 determines that the con- struction amount of the outdoor heat exchanger 41 is at the normal level, and accordingly, the output of the induction heater 60 P2 (S19).

When the room temperature is low under the same GAP condition, a larger amount of heat is required to remove the frost that has been frozen and has a larger conformational amount in the structure of the refrigeration cycle than in the case where the room temperature is higher. The heat quantity of the induction heater 60 can be maintained at least at the level of P2.

As described above, H1 to H8 are referred to as "first reference temperature" to "eighth reference temperature" as reference temperatures for judging the value of "outdoor temperature" - "outdoor heat exchanger pipe temperature" It will be possible. For example, H2 and H3 are referred to as a second reference temperature and a third reference temperature. As described above, the first reference temperature to the eighth reference temperature may be set to different values depending on the room temperature and the outdoor temperature value.

For convenience of explanation, T1, which is a criterion for determining the room temperature, is referred to as a "first set temperature", and T2 and T3, which are standards for determining the outdoor temperature, are referred to as a "second set temperature".

As in the above-described configuration, by detecting the indoor / outdoor temperature and the outdoor heat exchanger pipe temperature, judging whether there is a large or small congestion amount according to the difference between the outdoor temperature and the outdoor heat exchanger pipe temperature value and controlling the output of the induction heater, There is an advantage that it can be reduced.

That is, when the amount of the outdoor heat exchanger is large, the amount of heat generated by the induction heater is increased, and when the amount of the implantation is small, the amount of heat generated by the induction heater is reduced, thereby unnecessary waste of power consumption can be prevented.

FIG. 3 and FIG. 4 are flow charts showing a method in which an air conditioner according to an embodiment of the present invention is controlled for a first section of room temperature.

5 is a flow chart showing how the air conditioner is controlled for a second section of the room temperature.

Claims

A compressor for compressing the refrigerant;

An indoor heat exchanger for exchanging the refrigerant passing through the compressor with indoor air;

An expansion device for reducing the pressure of the refrigerant passing through the indoor heat exchanger;

An outdoor heat exchanger for exchanging heat with the refrigerant discharged from the expansion device;

A plurality of sensors for sensing a temperature of the outdoor air and a temperature of the outdoor heat exchanger;

A heater having a variable heating value according to the outdoor air temperature sensed by the sensor and the outdoor heat exchanger temperature;

A controller for determining an impregnation amount of the outdoor heat exchanger according to the difference between the outdoor air temperature and the outdoor heat exchanger temperature and controlling the output of the heater according to the impounding amount;

A gas-liquid separator provided at an inlet side of the compressor;

A bypass passage through which the refrigerant is bypassed from the outlet side of the compressor to the inlet side of the gas-liquid separator; And

And a first valve provided in the bypass passage for controlling the flow of the refrigerant.

The method according to claim 1,

Wherein the heater is an induction heater provided in the gas-liquid separator.

The method according to claim 1,

Wherein the bypass flow path is branched so that the refrigerant is bypassed from the outlet side of the compressor to the inlet side of the outdoor heat exchanger and the inlet side of the gas-liquid separator.

The method according to claim 1,

Wherein the amount of heat generated by the heater is increased as the temperature difference between the outdoor air temperature and the outdoor heat exchanger increases.

Comparing the room temperature with a preset first set temperature;

Comparing the outdoor temperature with a preset second preset temperature according to the indoor temperature;

Determining a temperature difference value between the outdoor temperature and the outdoor heat exchanger;

Comparing the temperature difference value with a preset reference temperature value; And

And controlling a calorific value of the heater according to a comparison result between the temperature difference value and the reference temperature value.

6. The method of claim 5,

Wherein the reference temperature value is previously set to a different value depending on whether the room temperature is equal to or higher than the first set temperature.

6. The method of claim 5,

Wherein the reference temperature value is previously set to a different value depending on whether the outdoor temperature is equal to or higher than the second set temperature.

6. The method of claim 5,

Wherein when the temperature difference value is larger than the reference temperature value, the heating value of the heater is increased.

6. The method of claim 5,

Wherein the output of the heater is adjustable to a first output value, a second output value smaller than the first output value, and a third output value smaller than the second output value,

Wherein when the outdoor temperature is lower than a predetermined value, the heater is controlled to output at least the second output value or more.

10. The method of claim 9,

Wherein when the room temperature is lower than the first set temperature, the heater is controlled to output at least the second output value or more.